str = 'Hello World!'
# 输出完整字符串
print(str)
# 输出字符串中的最后一个字符
print(str[-1])
# 输出字符串中第三个至第六个之间的字符串
print(str[2:5])
# 输出从第三个字符开始的字符串
print(str[2:])
# 输出字符串两次
print(str*2)

# 成员操作符 in not in
str1 = "hello"
str2 = "world"
print(str1 in str2)
print(str1 not in str2)

# 身份操作符  is:判断两个标识符是否指向同一地址 is not 相反
a = 20
b = 20
print(a is b)
print(a is not b)
b = 30
print(a is b)
print(a is not b)

# is is not  比较地址
# == !=  比较值


